Amperes measure the strength of a constant electric current that passes through two straight parallel conductors. They are located in a vacuum space at a distance of 1 meter from each other, the current causes a certain interaction force in the sections of the conductors. The ampere unit is called the magnetomotive force, which creates a closed loop in which a flow of electricity flows. The value is included in the seven basic SI units.
Content
- Historical background
- Current characteristic
- Ampere's law
Historical background
Ampere is a unit of measurement that was adopted in Paris at the first International Congress of Electricians in 1881. The magnitude got its name in honor of the famous physicist Andre Ampere. At that time, there was a unit that served as the definition of electricity in two dynes between two conductors. They are located at a distance of 1 cm from each other. Today this value is called bio or abumper.
The General Conference on Weights and Measures in 2011 decided that the main indicators of measurement will be redefined. Now, in the International System of Units, commonly used quantities should be based on the properties of atoms or physical constants, rather than on man-made artifacts.
Current characteristic
In the formal definition of the International Committee of Weights and Measures, amperes is the force of constant electricity flowing through thin long conductors. They must be in a vacuum with a distance of one meter.
Current causes interaction between conductors, the strength of which is equal to the product of the number 2 and 10 minus the seventh power for each meter section.
It is impossible to create such conditions in reality, because conductors have a certain length, as well as a cross-section. Therefore, the magnitude of the interaction is found by using coils on which many turns of wire have been wound. This method was used to calculate the standard of the unit on the balance of electric current. To determine what is equal to 1 ampere, we measured the moment of force that acted on a coil with directed electrons placed in a magnetic field.
In the Russian Federation, since 1992, the standard of ampere has been determined using Ohm's law, in an indirect way. With this calculation, the error is halved. The strength of the current is also represented as the rate of change of charge.
That is, 1 ampere is equal to the force of electricity at which a certain amount of it passes through the conductive element per second - one pendant.
The strength of the current can be found thanks to the formula: the ratio of electric charge to time. Designations of the quantities used:
- I - indicator of electricity;
- q is the charge;
- t - period.
Ampere's law
The French scientist Ampere not only contributed to the emergence of the name of the unit of measurement, but also established a certain physical law. It determines the strength of the effect of a uniform magnetic field on the conductor, which is placed in it.
Its value depends on the length of the current-carrying element in direct proportion. It also depends on the force of motion of directed electrons flowing in the conductor, the vector of magnetic induction and the sine of the angle between the direction of the first and second exponents.
The physicist was able to establish the conditions for the interaction of conductors with electric current. Their attraction or repulsion is due precisely to the directional movement of electrons. You can more accurately formulate the answer to the question of what the ampere is. This is the force of electricity at which parallel meter-long conductors interact in a vacuum.
It can be characterized by several processes:
- electricity passes in the heater up to 10 A;
- the lightning channel has a force of 500 kA;
- electrophoresis - 0.8 mA, with 1 mA = 0.001 A;
- 100 watt lamp on - 0.5 A.
In each section of the circuit, the current indicator is the same, since in a closed loop at any place through the cross-section of the conductor the same number of electrons flows every second. The value of the indicator does not depend on the thickness of the conductive element, because charges cannot accumulate in one area.
If you are interested in what the ampere will be in the future, then the answer was given in the last meeting of general conference. The quantity, as before, will determine the strength of the current, but at the same time it must depend on the new definition of the electric charge.
In addition to what is measured in amperes, you need to know the relationship of the value with other SI units. The voltage on the plates increases by one volt every second if a capacitor with a capacity of 1 farad is charged with electricity of one ampere. With a current strength of 1 A in the conductor, an electric charge of one coulomb passes through its cross section for every second. Additionally, this value is used to measure the difference in magnetic potential and magnetomotive force.
